The suitability of biotypes Q and B ofBemisia tabaci(Gennadius) (Hemiptera: Aleyrodidae) at different nymphal instars as hosts forEncarsia formosaGahan (Hymenoptera: Aphelinidae)

Abstract

Encarsia formosaGahan (Hymenoptera: Aphelinidae) is a solitary endoparasitoid that is commercially reared and released for augmentative biological control of whiteflies infesting greenhouse crops. In most areas in China, the invasive and destructive whiteflyBemisia tabaci(Gennadius) (Hemiptera: Aleyrodidae) biotype Q has replacedB. tabacibiotype B and has become dominant between the two. A better understanding of the suitability of different nymphal instars ofB. tabacibiotypes Q and B as hosts forE. formosais needed to improve the use of this parasitoid for biological control. Parasitism of the four nymphal instars ofB. tabacibiotypes Q and B by the commercial strain ofE. formosamass reared onTrialeurodes vaporariorum(Westwood) (Hemiptera: Aleyrodidae) was assessed in the laboratory. The results indicated thatE. formosaparasitized and successfully developed on all instars of both biotypes but performed best on the 3rd instar ofB. tabacibiotype B and on the 2nd, 3rd, and 4th instars ofB. tabacibiotype Q. The host-feeding rate of the adult parasitoid was generally higher on nymphal instars ofB. tabacibiotype Q than on the corresponding nymphal instars of biotype B and was significantly higher on the 2nd and 3rd instars. For both whitefly biotypes, the parasitoid’s immature developmental period was the longest on the 1st instar, intermediate on the 2nd and 3rd instars, and the shortest on the 4th instar. The parasitoid emergence rate was significantly lower on the 1st instar than on the other three instars and did not significantly differ betweenB. tabacibiotype B and biotype Q. Offspring longevity was greater on the 3rd and 4th instars than on the 1st instar and did not significantly differ between the twoB. tabacibiotypes. The results indicate that commercially-producedE. formosacan parasitize all instars ofB. tabacibiotypes B and Q, making this parasitoid a promising tool for the management of the two biotypes ofB. tabacipresent in China.